How to use 5G Dates Library

Description
This library contains 5G functions for dates. These functions can be used just like Excel's native functions. The library contains these functions:


CountDOWλ(Starts, Ends, DayOfWeek, [Diagnostics])
Count instances of a specific week day within two dates. Are you closed Sundays? How many Sundays are there next month?


CountDOWInMonthλ(DateInMonth, DayOfWeek, [Diagnostics])
Count instances of a specific week day within a month. Will the plant run Saturdays in July? How many Saturdays is that?



IsBetweenλ(Values, Low, High, [Inclusive], [Diagnostics])
Determine if a value (text, dates, numbers) is between a lower and upper limit. Why Excel doesn't have this is a mystery. 


IsOccurrenceDateλ(Dates, FirstOccurence, [LastOccurence], [Repeats], [Diagnostics])
Determine if a date passed is when a potentially repeating event happens. I use this for budgeting and projects.


OverLapDaysλ(Period1Start, Period1End, Period2Start, Period2End, [Diagnostics])
Return how many days overlap two period ranges. Rent by the day but bill by the week? This can help with that.


PeriodLabelλ(Date, [Interval], [Diagnostics])
Creates a label for a date based on period interval. Want reports with easy to read period headings? Use this.


Periodsλ(Starts, Ends, [Interval], [Diagnostics])
Determine the number of periods from date1 to date 2 inclusive. This is like the deprecated =DateDif() but better.


ScheduleRatesλ(PeriodEnds, RateStarts, Rates, [Diagnostics])
Schedules rates in a timeline from a start date until a new rate replaces it. Use this for rental rates, commission rates, etc.


ScheduleRatesByItemsλ(PeriodEnds, ItemFilter, ItemList, EffectiveList, RateList, [Diagnostics])
Schedules rates in a timeline from a start date until a new rate replaces it for each item in a list. 


ScheduleValuesλ(PeriodStarts, PeriodEnds, Values, EffectiveDates, [Diagnostics])
Schedules values in a timeline from a scheduled date table. Need to place asset acquisition costs in a timeline?


ScheduleValuesByItemsλ(PeriodStarts, PeriodEnds, ItemFilter, ItemList, EffectiveList, ValueList, [Diagnostics])
Schedules values in a timeline from a scheduled date table for each item in a list. Want to keep each asset in its own row?


Timelineλ(StartDate, Periods, Interval, PeriodStarts?, [Diagnostics])
Creates a horizontal list of start or end dates for a timeline. Timelines made easy and flexible.


About 5G
5G is, perhaps, the most significant advance in financial modeling since the introduction of financial modeling standards. That is quite a bold statement. After all, we have Python, Power Query, Power Pivot, Dynamic Arrays, and LAMBDAs. So what makes 5G more impactful to financial modeling than them?

Assembling Models from Pre-Built, Pre-Tested Components vs Creating Models from Individual Formulas
5G is a standard for creating LAMBDAs. 5G is short for fifth generation modeling which is based on assembling models from components rather than hand writing individual formulas. This technique is called "Component Based Development" or CBD. CBD's benefits have been the subject of several empirical studies that verify CBD can increase productivity by 50%, and decrease defects by 50%. CBD has been around for decades but it wasn't until the introduction of LAMBDA and Microsoft's Advanced Formula Environment that CBD could be practiced with Excel's formulas.

Dynamic Arrays and Corkscrew Accounts
5G is especially important to Financial Modeling because of Dynamic Arrays. Dynamic arrays reduce potential points of failure in models by orders of magnitude. They make models more responsive and more flexible. Dynamic arrays speed development by eliminating the copy-to-right step in writing model calculations. And for 90% of model calculations, dynamic array formulas are simpler than traditional formulas. When dynamic arrays were introduced, it appeared they would quickly takeover the financial modeling world until it became apparent they didn't work for one of the most common structures in financial modeling, the common corkscrew account.

5G Makes the Dream of Dynamic Models a Reality
Dynamic arrays, on their own, cannot perform any corkscrew calculation. For dynamic arrays to perform corkscrew calculations requires LAMBDA, but LAMBDA is an advanced Excel skill and most financial modelers are not Excel experts. Many are Excel novices. 5G turns LAMBDAs, even dynamic array corkscrew LAMBDAs, into simple functions anyone can use.

5G Eliminates Circularity
5G functions not only master the common corkscrew, they also eliminate circular references that plague certain advanced financial model calculations such as debt sculpting with interest averaging. With 5G, even Excel novices can include these advanced calculations in their models because 5G functions look and act like Excel's native functions.  

Summary
So what makes 5G more impactful to financial modeling than Python, Power Query, Power Pivot, Dynamic Arrays, and LAMBDA?
1) 5G is aimed at the core of modeling - the model; not analytics or visuals, like Python; not data, like Power Query, and not just aggregations like Power Pivot.
2) Dynamic Arrays in financial models need LAMBDAs to perform common calculations like corkscrews, and advanced calculations that require circularity.
3) 5G makes LAMBDAs usable by novices.
4) 5G, on its own, has the power to increase modeler productivity by 50% and reduce model defects by 50%. Dynamic arrays with 5G LAMBDAs can improve both of those measures considerably.

5G creates functions anyone can use to solve complex financial modeling problems quickly, correctly, and easily.